Template:Infobox helium

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Helium,  2He
Helium discharge tube.jpg
General properties
Appearance colorless gas, exhibitin a reid-orange glow when placed in a heich-voltage electric field
Staundart atomic wecht (Ar, staundart) 4.002602(2)[1]
Helium in the periodic cairt
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Airn Cobalt Nickel Capper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Siller (element) Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gowd Mercur (element) Thallium Leid (element) Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Ununtrium Flerovium Ununpentium Livermorium Ununseptium Ununoctium
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He

Ne
hydrogenheliumlithium
Atomic nummer (Z) 2
Group group 18 (noble gases)
Period period 1
Element category   noble gas
Block s-block
Electron confeeguration 1s2
Electrons per shell
2
Pheesical properties
Phase (at STP) gas
Meltin pynt (at 2.5 MPa) 0.95 K ​(−272.20 °C, ​−457.96 °F)
Bylin pynt 4.22 K ​(−268.93 °C, ​−452.07 °F)
Density (at STP) 0.1786 g/L
when liquid (at m.p.) 0.145 g/cm3
when liquid (at b.p.) 0.125 g/cm3
Creetical pynt 5.19 K, 0.227 MPa
Heat o fusion 0.0138 kJ/mol
Heat o vapourisation 0.0829 kJ/mol
Molar heat capacity 5R/2 = 20.786 J/(mol·K)
Vapour pressur (defined bi ITS-90)
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K)     1.23 1.67 2.48 4.21
Atomic properties
Oxidation states 0
Electronegativity Pauling scale: no data
Covalent radius 28 pm
Van der Waals radius 140 pm
Coloyr lines in a spectral range
Spectral lines o Infobox helium
Miscellanea
Creestal structurhexagonal close-packed (hcp)
Hexagonal close-packed creestal structur for helium
Speed o soond 972 m/s
Thermal conductivity 0.1513 W/(m·K)
Magnetic orderin diamagnetic[2]
CAS Nummer 7440-59-7
History
Diskivery Pierre Janssen, Norman Lockyer (1868)
First isolation William Ramsay, Per Teodor Cleve, Abraham Langlet (1895)
Main isotopes o helium
Iso­tope Abun­dance Hauf-life (t1/2) Decay mode Pro­duct
3He 0.000137%* stable
4He 99.999863%* stable
  • Atmospheric value, abundance mey differ elsewhaur.
| references | in Wikidata

References

Thir references will appear in the airticle, but this list appears anerly on this page.
  1. Meija, J.; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305. 
  2. Magnetic susceptibility of the elements and inorganic compounds, in Handbook of Chemistry and Physics 81st edition, CRC press.